Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
  • B60C1/0025—Compositions of the sidewalls
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/5406—Silicon-containing compounds containing elements other than oxygen or nitrogen
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
  • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 

Definitions

• the present invention relates to a rubber composition for tire sidewall and a tire prepared therefrom.
• tread rubber portion which causes 50 to 60% of hesteresis loss of tire. Due to recent developments with respect to polymer and carbon black and improvements with respect to blending technique including them, the hesteresis loss of the tread rubber portion has been decreased to 30 to 40% and thereby, rolling resistance of tire is also decreased remarkably.
• the inventor of the present invention gave his attention to tire sidewall portion and has found that rolling resistance of tire can be lowered without lowering wear resistance and WET property of the tread portion and without increasing electric resistance of a whole tire by using the particular kind of carbon black as carbon black for reinforcement of the sidewall portion, replacing a part of the carbon black with the particular kind of silica, and particularly using the specific amount of silane coupling agent together.
• an object of the present invention is to provide a rubber composition for tire sidewall which gives a tire having low rolling resistance, excellent wear resistance and WET property, and low electric resistance.
• the present invention relates to a rubber composition obtained by kneading
• At least one diene rubber selected from the group consisting of natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber and ethylene-propylene-diene terpolymer, cetyltrimethyl ammonium bromide 5 to 50 parts of a carbon black having an average particle size of primary particle of not less than 20 nm, a compression dibutyl phthalate (DBP) oil absorption number of not more than 120 ml/100 g and a Cetyl Trimethyl Ammonium Bromide (hereinafter referred to as "CTAB”) specific surface area of not more than 130 m 2 /g, 10 to 60 parts of a precipitated silica having a DBP oil absorption number of not less than 200 ml/100 g,
• DBP compression dibutyl phthalate
• CTAB Cetyl Trimethyl Ammonium Bromide
• BET Brunauer Emmett Teller
• X is a mixing amount of silane coupling agent (unit is parts by weight) per 100 parts of the precipitated silica
• A is the number (unit is per nm 2 ) of silanol groups existing per 1 nm 2 of surface area of the precipitated silica
• B is BET nitrogen adsorption specific surface area (unit is m 2 /g) of the precipitated silica
• C is a factor showing reactivity of the silane coupling agent to the precipitated silica
• D is a molecular weight of the silane copuling agent
• E is Avogadro's constant (6.022 ⁇ 10 23 ).
• the present invention relates to a tire of which the sidewall portion is prepared from the above-mentioned rubber composition for tire sidewall.
• 100 parts of the diene rubber comprises not less than 30 parts of natural rubber, and that the diene rubber comprises natural rubber and a butadiene rubber having a high cis content.
• silane coupling agent bis(triethoxysilylpropyl)tetrasulfide is preferably used.
• silicas used for tire there are, for example, precipitated silica (so-called hydrosilicate), Aerosil (silicic anhydride) and a silicate such as clay or talc.
• precipitated silica si-called hydrosilicate
• Aerosil silicic anhydride
• a silicate such as clay or talc.
• the precipitated silica having the above-mentioned particular properties is used from viewpoints of high dispersibility into rubber and high reinforcing ability for a rubber composition to be obtained.
• a DBP oil absorption number of the precipitated silica is not less than 200 ml/100 g from viewpoints that dispersiability into a rubber composition for tire sidewall is improved and that hesteresis loss of the obtained tire is decreased, and is preferably 200 to 350 ml/100 g, more preferably 200 to 280 ml/100 g.
• a BET nitrogen adsorption specific surface area of the precipitated silica is not more than 180 m 2 /g from viewpoints that a mixing amount of the silane coupling agent described below can be decreased and that hesteresis loss of the obtained tire is decreased, and is preferably 50 to 180 m 2 /g, more preferably 50 to 100 m 2 /g.
• precipitated silica having the above-mentioned properties
• commercially available examples are, for instance, Ultrasil VN3, Ultrasil FK160, DUROSIL available from DEGUSSA, and the like.
• An average particle size of primary particle of the carbon black used in the present invention is not less than 20 nm from viewpoints that energy loss of tire decreases, that rolling resistance of tire is lowered and that good reinforcing ability can be obtained, and is preferably 25 to 60 nm, more preferably 30 to 50 nm.
• a compression DBP oil absorption number of the carbon black is not more than 120 ml/100 g from viewpoints that structure becomes large and that tan ⁇ is decreased, and is preferably 80 to 120 ml/100 g, more preferably 80 to 100 ml/100 g.
• a CTAB surface area of the carbon black is not more than 130 m 2 /g from a viewpoint that energy loss of tire is decreased, and is preferably 40 to 125 m 2 /g, more preferably 40 to 80 m 2 /g.
• Examples of the carbon black having the above-mentioned properties are, for instance, FEF, HAF, ISAF, N339, N351, and the like.
• the specific amount of silane coupling agent is used so that the precipitated silica disperses into the rubber composition more homogeneously and wear resistance of tire to be obtained is ensured.
• silane coupling agent examples include, for instance, bis(triethoxysilylpropyl)tetrasulfide, triethoxysilylpropylisocyanate, vinyltriethoxysilane, vinyltrimethoxysilane, ⁇ -methacryloxypropyltrimethoxysilane, ⁇ -methacryloxypropylmethyldimethoxysilane, ⁇ -glycidoxypropylmethyldiethoxysilane, ⁇ -mercaptopropyltrimethoxysilane, ⁇ -(polyethylene amino)-1-propyltrimethoxysilane, N- ⁇ -(aminoethyl)- ⁇ -aminopropyltrimethoxysilane, salt of N'-vinylbenzyl-N-trimethoxysilylpropylethylenediamine, and the like.
• bis(triethoxysilylpropyl)tetrasulfide, triethoxysilylpropylisocyanate and ⁇ -mercaptpropyltrimethoxysilane are preferable, and bis(triethoxysilylpropyl)tetrasulfide is most preferable.
• diene rubber used in the present invention examples are, for instance, natural rubber (hereinafter referred to also as “NR”), butadiene rubber (hereinafter referred to also as “BR”), styrene-butadiene rubber (hereinafter referred to also as “SBR”), isoprene rubber (hereinafter referred to also as “IR”), ethylene-propyrene-dieneterpolymer (hereinafter referred to also as “EPDM”), and the like.
• NR natural rubber
• BR butadiene rubber
• SBR styrene-butadiene rubber
• IR isoprene rubber
• EPDM ethylene-propyrene-dieneterpolymer
• the diene rubber can be used alone, or in admixture of two or more.
• SBR styrene-butadiene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrenethacrylate graft copolymerization (hereinafter referred to also as "S-SBR”), and the like.
• E-SBR emulsion polymerization
• S-SBR solution polymerization
• NR, BR, S-SBR, EPDM combination of NR and BR, combination of NR, BR and S-SBR, and combination of NR, BR and EPDM are preferable.
• a cis content of the BR is high, for example not less than 20% by weight, more preferably not less than 30% by weight from a viewpoint that cracking and cut-growth resistance to bending of tire can be obtained.
• each of the precipitated silica and carbon black has function as reinforcement for tire. Further, dispersibility of the precipitated silica is improved by using the silane coupling agent.
• the rubber composition of the present invention is obtained by kneading the above-mentioned rubber reinforcing components with the diene rubber.
• a mixing ratio of the precipitated silica is 10 to 60 parts, preferably 10 to 40 parts, more preferably 20 to 40 parts per 100 parts of the diene rubber.
• a mixing amount of the carbon black is 5 to 50 parts, preferably 5 to 30 parts, more preferably 10 to 20 parts per 100 parts of the diene rubber.
• C is a factor (hereinafter referred to as "reactive factor") showing reactivity (coupling effect) of the silane coupling agent to the precipitated silica.
• reactive factor a factor showing reactivity (coupling effect) of the silane coupling agent to the precipitated silica.
• the reactive factor C is a factor which has been found by the inventor of the present invention as a result of many experiments in which the mixing amount of the silane coupling agent to the precipitated silica varied to give various rubber compositions and various characteristics of the obtained rubber compositions were investigated and then an optimum range for the mixing amount of the silane coupling agent to the precipitated silica was determined.
• the reason why the mixing amount of the silane coupling agent is limited in such a range is that reinforcing ability can be improved and, namely, wear resistance of the obtained tire is ensured by enhancing coupling effect with the diene rubber. It is noted that to enhance the coupling effect of the silica with the diene rubber leads to improvement of dispersibility of the silica into the diene rubber.
• 100 parts of the diene rubber comprises not less than 30 parts of NR from viewpoints that rolling resistance becomes lowered and that surface appearance of extruded rubber article are good, and is preferably 30 to 80 parts, more preferably 40 to 70 parts.
• the diene rubber when a combination of NR and the other diene rubber is used as the diene rubber, it is preferable to use the BR having a high cis content from a viewpoint that cracking and cut-growth resistance to bending can be obtained.
• a mixing amount of such a BR is preferably 30 to 70 part, more preferably 40 to 60 parts in 100 parts of the diene rubber.
• the precipitated silica is previously reacted with the silane coupling agent, a tire superior particularly in rolling resistance and weather resistance can be obtained.
• a banbury mixer is charged with a given amount of the diene rubber, a given amount of the precipitated silica and a given amount of the silane coupling agent, a part of a given amount of the carbon black and a part of oil and the components are mixed for 1 to 5 minutes at a temperature of 130° to 160° C. Then, residual amounts of the carbon black, oil and various kinds of processing aid are added and kneaded for 1 to 5 minutes at a temperature of not higher than 140° C. At last, a vulcanizing agent, an accelerator and the like are added and kneaded for 1 to 5 minutes at a temperature of not higher than 100° C. to obtain a rubber composition for tire sidewall of the present invention.
• a toluene-swollen degree (%) of a vulcanized rubber which is obtained by vulcanizing the rubber composition for tire sidewall of the present invention at 140° to 190° C., preferably 145° to 185° C. for 5 to 60 minutes, preferably 8 to 50 minutes in an ordinary manner, is preferably not less than 200 and less than 450, more preferably not less than 250 and less than 400.
• the toluene-swollen degree is determined by sinking a sample rubber completely into toluene, allowing the sinking sample to stand for 24 hours, taking the sample out of toluene, wiping the sample properly, measuring the weight Y of the sample and then substituting Y into the equation: (Y/10) ⁇ 100%.
• a vulcanizer such as sulfur, an accelerator, an antiaging agent, an antioxidant, a softener, a vulcanization accelerator such as stearic acid, a processing aid can be mixed optionally in a range wherein the effects of the present invention are not affected.
• the present invention also relates to a tire wherein a sidewall portion is prepared from the rubber composition of the present invention.
• the silica when the silica is mixed in a rubber composition for tread instead of a carbon black which is a transferring material for static electricity generated by friction between a tire and road, the static electricity is not tranferred and accumulated in the tread portion.
• the silica is mixed in the sidewall portion, not in the tread portion, and the static electricity can be discharged from the tread portion to outside of the tire through a steel belt rubber layer and a case cord rubber layer.
• a compound in which somewhat a lot, namely not less than 30 parts, of carbon black is blended per 100 parts of rubber component can be adopted.
• chopped fibers obtained by cutting fine fibers of nylon or polyester on which polypyrrole or polyaniline is carried to 0.5 to 4 mm length can be mixed, or fillers such as silica on which polypyrrole or polyaniline is carried can be also used.
• This composition is advantageous in such points of low rolling resistance, good cut resistance, and good steering stability.
• This composition is superior in such points of low rolling resistance, good cut resistance and riding good comfort.
• a banbury mixer is charged with the diene rubber, the precipitated silica and the silane coupling agent and a part of a given amount of the carbon black. After the mixture is kneaded for 1 to 5 minutes at a temperature of 130° to 160° C., the obtained rubber is taken out once and cooled.
• the banbury mixer is charged with the obtained rubber and the residual carbon black and oil in order and the mixture is kneaded for 1 to 5 minutes at a temperature of not higher than 140° C.
• the rubber was then taken out and cooled again.
• a vulcanizer and the like are added at a temperature of not higher than 100° C. and kneaded for 1 to 5 minutes with the banbury mixer or an open roll to obtain the rubber composition for tire sidewall of the present invention.
• a tire was produced in an ordinary manner by using the obtained rubber composition and was subjected to the following tests. The results of the tests are shown in Table 1.
• the following rubber blend having a low electric resistance was used as the rubber composition for tread portion.
• Hs Hardness of rubber
• E* and tan ⁇ were determined at 70° C. and with 20% of dynamic stress by means of Viscoelastic Spectrometer available from Kabushiki Kaisha Iwamoto Seisakusho.
• Cracking growth was measured by means of Demattia Bending Cracking Resistance Test Machine available from Kabushiki Kaisha Ueshima Seisakusho according to JIS K 6260, and cracking and cut-growth resistance to bending was evaluated as A when cracking growth was not less than 1 million times/min, B when 5 hundred thousand to 1 million times/min, and C when not more than 5 hundred thousand times/min.
• Axial tension was measured by means of Rolling Resistance Testing Machine available from Kobe Kikai Kabushiki Kaisha according to JIS. Then, rolling resistance was determined by the following equation. ##EQU3## The obtained rolling resistance is expressed as index on the basis of the rolling resistance obtained in Experimental Example 7 (in which the precipitated silica and the silane coupling agent are not mixed).
• a rubber composition and a tire were prepared in the same manner as in Experimental Example 1 except that components and mixing amounts shown in Table 2 were adopted but the precipitated silica and silane coupling agent were not blended.
• the obtained rubber composition and tire were subjected to the same tests as in Experimental Example 1. The results were shown in Table 2.
• Rubber compositions and tires were prepared in the same manner as in Experimental Example 1 except that the components and mixing amounts shown in Table 2 were adopted. The obtained rubber compositions and tires were subjected to the same tests as in Experimental Example 1. The results were shown in Table 2.
• N351 available from Showa Cabot Co., Ltd. (average particle size of primary particle: 28 nm, CTAB surface area: 82 m 2 /g, compression DBP oil absorption number: 97 to 105 ml/100 g)
• FK160 available from DEGUSSA BET nitrogen adsorption specific surface area: 160 m 2 /g, DBP oil absorption number: 250 ml/100 g, number of silanol groups per nm 2 surface area: 2.6
• DUROSIL available from DEGUSSA. (BET nitrogen adsorption specific surface area: 60 m 2 /g, DBP oil absorption number: 220 ml/100 g, number of silanol groups per nm 2 surface area: 2.6)
• the rubber composition for tire sidewall of the present invention provides a tire having superior wear resistance, WET property, lowered rolling resistance, cracking and cut-growth resistance to bending and cut resistance.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Tires In General (AREA)

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Citations (3)

• 1997
  • 1997-04-17 US US08/843,916 patent/US5929157A/en not_active Expired - Lifetime
  • 1997-04-21 EP EP97302717A patent/EP0803535B1/de not_active Expired - Lifetime
  • 1997-04-21 DE DE69705579T patent/DE69705579T2/de not_active Expired - Lifetime

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